Defence responses of Norway spruce seedlings to elicitors of ectomycorrhizal fungus Pisolithus tinctorius and pathogen Heterobasidion annosum are affected by zeatin riboside | Vpliv zeatin ribozida na obrambni odgovor kalic smreke po tretiranju z elicitorji mikorizne glive Pisolithus tinctorius in patogena Heterobasidion annosum

anglais. Cytokinins are known to attenuate defence responses of plants after elicitor application or inoculation with fungi. To evaluate their role in the regulation of colonisation of Norway spruce (Picea abies) seedlings with mycorrhizal and pathogenic fungus, we analysed the effects of zeatin riboside (ZR) on: i) growth of ectomycorrhizal fungus Pisolithus tinctorius and pathogen Heterobasidion annosum in axenic cultures, ii) colonisation intensity of selected fungi on P. abies seedlings and iii) induction of defence reactions of spruce seedlings following elicitor treatment. Mycorrhizal fungus P. tinctorius showed increased growth at concentrations higherthan 10-2 µM ZR that was accompanied by increased ergosterol concentrations. In contrast, decreased growth of pathogen H. annosum was observed at the highest ZR (10 µM) concentration. ZR treatment also increased colonisation of spruce seedlingswith the mycorrhizal fungus. Application of cell wall preparations of both fungi increased peroxidase (POD) activity in the roots of treated spruce seedlings, whereas only elicitors of H. annosum increased also phenylalanine ammonia-lyase (PAL) activity,levels of soluble phenolics and salicylic acis (SA) concentrations. Application of ZR negated the increased activity of POD that was observed in elicitor treated seedlings, accompanied by increased levels of soluble phenolics in the roots of elicitated seedlings. In contrast, no effects of ZR treatment on PAL activity and SA accumulation could be observed. Our results suggest involvement of ZR in the regulation of cell wall modifications during the fungal colonisation with P. tinctorius and formation of ectomycorrhizae, by affecting the growth of fungal partner and non-specific defence reactions of the plant host.

slovène. Iz literature je znano, da lahko citokinini vplivajo na obrambne reakcije rastlin, ki se sprožijo po aplikaciji elicitorjev ali ob inokulaciji z živo glivo. Za ovrednotenje njihove vloge pri regulaciji kolonizacije kalic smreke (Picea abies) z mikoriznimi in patogenimi glivami, smo preverili vpliv zeatin ribozida (ZR): i) na rast ektomikorizne glive Pisolithus tintorius in patogena Heterobasidion annosum v aksenični kulturi, ii) na stopnjo kolonizacije kalic smreke z obema glivama in iii) na aktivacijo obrambnih reakcij smreke po tretiranju z elicitorji. V aksenični kulturi smo pri 10-2 µM koncentraciji ZR opazili pospešeno rast mikorizne glive P. tinctorius, ki jo je spremljala povečana koncentracija ergosterola v miceliju. Nasprotno je bila rast patogene glive H. annosum pri najvišji koncentraciji ZR v gojišču (10 µM) zavrta. Podobno kot v aksenični kulturi je dodaten ZR pospešil kolonizacijo kalic smreke z ektomikorizno glivo, medtem ko na stopnjo kolonizacije s patogenom ni imel učinka. Tretiranje smreke z elicitorji obeh gliv je povečalo aktivnost peroksidaz (POD) v koreninah kalic, samo elicitorji patogene glive H. annosum pa so povečali tudi aktivnost fenilalanin amonijeve liaze (PAL) in koncentracijo topnih fenolov ter proste salicilne kisline (SA). Dodatek ZR je znižal peroksidazno aktivnost v kalicahtretiranih z elicitorji obeh gliv in povečal koncentracijo topnih fenolov. Nasprotno, ZR ni imel nobenega vpliva na aktivnost PAL in akumulacijo salicilne kisline v koreninah smreke. Na podlagi naših rezultatov predvidevamo, da je ZR vpleten v regulacijomodifikacij celične stene ob glivni kolonizaciji z ektomikorizno glivo P. tinctorius in vzpostavitev ektomikorize, preko delovanja na glivnega partnerja in nespecifične obrambne reakcije gostitelja.